The present invention relates to high speed line printers, and especially to the paper stacker assembly for stacking paper in a bin in a high speed line printer.
In the impact printing field, a wide variety of printing techniques have been utilized in the past, including the present type of printer, which uses an endless steel character band having various characters of the alphabet as well as numbers embossed or raised upon the band. The band is rotated between a drive pulley and an idler pulley. As the band is driven at high speeds adjacent a platen, a bank of parallel hammers is driven at high speed at the moment that a particular desired character is passing on the band to print the characters on the paper. Inasmuch as a bank of print hammer actuators is fired electromagnetically as the band is passing at high speed, printing is accomplished at a very high speed so that the paper being printed upon is rapidly passing over the platen and being printed upon and fed into a stacker assembly, typically located in the rear of the printer, which must stack the paper evenly in folds. Controls are provided to indicate when the stacker bin is filled, as well as means to hold the paper compacted in the bin. In a stacker assembly of the present type, an elevator is mounted therein and rides on a shaft and is raised and lowered by an electric motor driving a cog belt or the like. The motor raises or lowers the elevator responsive to controls from the microprocessor of the high speed printer, which generates signals in accordance with the position of the elevator and the paper as the paper is fed into the bin.
In prior stacker assemblies, it has been known to compact the paper in the bin by the use of flexible belts mounted on either side of the paper bin having flexible flaps thereon which are rotated to compact the paper. It has also been known in the past to vary the speed of an elevator in accordance with the speed of the printing and the thickness of the paper so that the elevator continuously moves at a predetermined speed. Other techniques involve the use of photo cells for detecting the position of materials in bins. The present invention, on the other hand, utilizes simple mechanical sensors generating electrical pulses which operate an elevator in accordance with signals generated in a printer microprocessor.